The "Low Tech Magazine" has a guide to building a DIY bike generator https://solar.lowtechmagazine.com/2022/03/how-to-build-a-pra...

Unfortunately even with the bike it seems like you really need to find one machine that can be repurposed, a rowing machine seems a bit of a stretch.

For reference, this is what 700W cycling looks like: https://www.youtube.com/watch?v=S4O5voOCqAQ

It’s basically well known to cyclists that training with a power meter that tells you “watts” more accurately gauges effort and caloric expenditure. (Heart rate gauges subjective effort however, taking into account stress, caffeine intake, etc.)

It’s also interesting that the industry has settled on using watts to mean rate of useful work whereas calories to mean the total work including inefficiencies, despite that calories is just a unit of energy. A rule of thumb for cyclists is that in addition to usual unit conversions, the “calories” figure should be multiplied by four to account for energy expended by the body but not used for rotating the pedals. I don’t use rowing machines but I’m sure they would have a similar conversion factor in order to calculate calories.

"Please row faster, the model is thinking" is the future of human-in-the-loop.

You can get a dynamo hub front wheel for push bikes: https://bikepacking.com/plan/dynamo-hubs-lighting-charging-g...

However you can expect around only 3 watts of output at normal speeds and you will need to put in around 5-7 watts of power for the same speed. This is barely enough to trickle charge modern phones.

> got me wondering if they made rowing machines that could slowly charge a battery

The Concept2 rowing machines can power itself using the power you generate by rowing, so we're partly there.

> offered "watts" as a unit of how hard you're going (like "calories" or "mph")

It's the only unit that makes sense tbh

Soon enough we will see rowing machines rated in max TFLOPS.

A fairly untrained cyclist is usually able to maintain 200W, so yes this is definitely possible

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